Intermittent severe transfer speed issues to GitHub CDN

There have been ongoing network performance issue that have been occurring intermittently for several weeks and appear to be related to peering or congestion between your network and GitHub’s CDN.  The problem is not general connectivity, latency, or packet loss as those all appear normal, but rather severe and intermittent slow transfer speeds, specifically when transferring larger amounts of data from GitHub’s CDN edge network.

Issue:

Sustained downloads from GitHub’s CDN endpoints (IP range 185.199.108.0/22) frequently drop to approximately 1–2 MB/s for extended periods, even though:

• Latency to the destination is low (~10–15 ms)

• Packet loss is 0%

• MTU and path MTU are correct

• Other large downloads from non-GitHub destinations run at full speed

• The same GitHub resources are fast at other times, without any local changes

This issue has been happening intermittently but frequently for multiple weeks, and it seems to affect larger transfers (hundreds of megabytes or more). Small requests and handshakes are fast, resulting in ping, traceroute, or basic connectivity tests not identifying the issue.

GitHub and its associated registries (including ghcr.io and githubassets.com) are critical for many technical work-from-home activities. When this issue occurs, it dramatically slows down or stalls work.  While this is not technically an "outage", it's a significant issue that can seriously impact those who rely on GitHub-hosted assets.

Summary:

• Affected destination example:

  • cdn-185-199-110-154.github.com (185.199.110.154)

• Symptom: Very low sustained throughput (~1–2 MB/s) for large HTTPS transfers

• Latency: Normal

• Packet loss: None observed

• MTU: Verified correct

• DNS: Verified consistent across resolvers

The issue seems consistent with congestion, suboptimal routing, or saturation on the path between Comcast and GitHub’s CDN, rather than anything local.

Could you please look into if there are issues between your network and GitHub’s CDN (I'm in SE Michigan)?

I’m happy to provide any additional information are diagnostics that would be helpful in resolving the issue.  Thank you.